1. Field of the Invention
The present invention relates to a method for fabricating a semiconductor device, and more particularly to a method for forming a metal wiring in a semiconductor device in order to improve an operational speed of the semiconductor device.
2. Description of the Prior Art
As generally known in the art, aluminum or tungsten is mainly used as a material for a metal wiring. In particular, since a tungsten layer, which is deposited on a substrate through a chemical vapor deposition (CVD) process, represents the superior gap-filling characteristic and the low resistivity, the tungsten layer is mainly used for fabricating highly integrated semiconductor devices.
FIGS. 1a and 1b are cross-sectional views illustrating a conventional procedure for forming a metal wiring in a semiconductor device.
As shown in FIG. 1a, an interlayer dielectric film 11 is formed on a silicon substrate 10 having a predetermined base structure and a contact hole 12 for exposing a predetermined portion of the silicon substrate 10 is formed by selectively etching the interlayer dielectric film 11. In addition, a barrier layer 13 is formed on the interlayer dielectric film 11 including the contact hole 12. The barrier layer 13 has a stacked structure including a Ti layer and a TiN layer stacked on the Ti layer. Then, the silicon substrate 10 formed with the barrier layer 13 is subject to the rapid heat-treatment process, thereby forming a TiSix layer 14 on an interfacial surface between the barrier layer 13 and the silicon substrate 10.
After that, a first tungsten layer 15 is formed on the barrier layer 13. When forming the first tungsten layer 15 on the barrier layer 13, WF6 is used as a source gas and SiH4 is used as a reaction gas for the first tungsten layer 15. Then, a second tungsten layer 16, that is, a tungsten bulk layer is formed on the first tungsten layer 15 in such a manner that the contact hole 12 is filled with the second tungsten layer 16. When forming the second tungsten layer 16 on the first tungsten layer 15, WF6 is used as a source gas and H2 is used as a reaction gas for the second tungsten layer 16.
As shown in FIG. 1b, a metal wiring 17 is formed by selectively etching the second tungsten layer 16, the first tungsten layer 15, and the barrier layer 13. Reference numerals 13a, 15a and 16a represent a remaining barrier layer, a remaining first tungsten layer and a remaining second tungsten layer, respectively, which may remain after the etching process has been completed.
However, as the integration degree of the semiconductor device has been increased, the conventional procedure for forming the metal wiring 17 in the semiconductor device represents a limitation to reduce the resistance of the metal wiring 17 even if tungsten having the low resistivity is used as a material for the metal wiring 17. For this reason, the operational speed of the semiconductor device is significantly reduced.